1. Field
Aspects of embodiments of the present invention are directed toward an organic light emitting diode (OLED) display.
2. Description of the Related Art
Among the display devices, the organic light emitting diode (OLED) display is a self-light-emitting display; that is, it does not require a separate light source. Therefore, it has lower power consumption than non-self-light-emitting displays, and response speed, viewing angle, and contrast ratio of the organic light emitting diode (OLED) display are excellent.
The organic light emitting diode (OLED) display includes a plurality of pixels such as red color pixels, blue color pixels, green color pixels, and white pixels (white color pixels), and may express a full range of colors by combining the different color pixels. Each pixel includes a light emitting element and a plurality of thin film transistors for driving the light emitting element.
The light emitting element of the organic light emitting diode (OLED) display includes a pixel electrode, a common electrode, and an emission layer between the two electrodes. Either the pixel electrode or the common electrode is an anode, and the other of the pixel electrode or the common electrode is a cathode. Electrons injected from the cathode and holes injected from the anode are coupled with each other (that is, joined) in the light emitting layer to form excitons, and the excitons emit light while discharging energy. The common electrode is formed throughout a plurality of pixels to transfer a common voltage.
The OLED display may be a bottom emission display, in which light is emitted toward a bottom thereof, or a top emission display, in which light is emitted toward a top thereof. In the top emission OLED display, the common electrode may include a transparent conductive material, and in the bottom emission OLED display, the common electrode may include opaque conductive material.
External light entering from the outside of the OLED display may be reflected by the surface of the OLED display or by various internal layers of the OLED display, thereby reducing visibility and quality of an image. For example, when the external light is reflected, visibility of black color is decreased, thereby causing a decrease in a contrast ratio. Therefore, a polarizer may be attached at a peripheral area of an interface (or boundary) where the OLED display meets an external environment so as to reduce reflection of the external light.
In addition, because the OLED display has a multi-layered structure, light generated from the emission layer may be kept in (that is, may remain in) an internal layer of the OLED display rather than being emitted outwards. For example, when the polarizer is attached to an external side of the OLED display, light generated in the emission layer may be absorbed or reflected by the polarizer, such that light extraction efficiency of the OLED display may be significantly reduced.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.